NGC 7331 is an unbarred spiral galaxy in the constellation Pegasus, about 46 million light years from us. It has a diameter of around 140,000 light years, putting it in a similar league to our Milky Way in terms of size — though with characteristic differences. You can see a bright core, pronounced dust lanes and clearly recognisable spiral arms.
In July 2025 the supernova SN 2025rbs, of type Ia, was discovered in NGC 7331 — initially relatively faint (~17.07 mag), but later brightening to about 14.4 mag.
Next to NGC 7331 in the field of view is Stephan’s Quintet, a compact group of galaxies about 270–300 million light years away. Four of the galaxies are gravitationally bound and interacting, which leads to shock fronts and gas streams. A fifth visible member, NGC 7320, sits in the foreground — at only about 40 million ly — and does not belong to the dynamically connected group.
NGC 7315 and several fainter background galaxies are also visible.
| IMAGE DATA | |
|---|---|
| Object | NGC7331 / Stephan’s Quintett |
| Distance | approx. 46 bzw. 300 million light years |
| Date | 03. & 18.09.2025 |
| Exposure | RGB each 26x 120sec., Luminance 85x 180sec. & Halpha 104x 300sec. - Total approx. 15.5h |
| Mount | Skywatcher EQ6-R Pro |
| Telescope | Askar 120APO with 0.8x Reducer |
| Camera | ZWO ASI 2600mm with ZWO HA+LRGB Filter |
| Guiding | Zwo Asi OAG with ZWO Asi 290mm Mini & Asiair |
| Software | AsiAir, Astropixel Processor, Pixinsight, Photoshop CC, NoiseXterminator, Star X Terminator, BlurXterminator, Nik Collection 7 |